Metal‐CO ₂ Batteries: By‐Product Challenges and Practical Pathways for Low CO ₂ Concentration Environment

ABSTRACT Metal‐CO 2 batteries have recently emerged as an intriguing class of energy storage and conversion devices that simultaneously utilize and manage carbon dioxide. Originating from studies of CO 2 contamination in metal‐air batteries, these systems have evolved into a distinct research direction, offering insights into CO 2 electrochemistry and its potential for sustainable energy technologies. Despite notable advances, their progress toward practical applications is fundamentally limited by the formation and decomposition of insoluble by‐products such as carbonates and amorphous carbon, which govern rechargeability, efficiency, and long‐term stability. This review critically examines recent progress in metal‐CO 2 batteries with an emphasis on discharge and charge mechanisms, the formation and evolution of solid by‐products, and the experimental limitations associated with closed‐cell configurations. We summarize key mechanistic insights reported for different metal‐CO 2 systems and discuss how catalyst composition and electronic structure influence adsorption behavior, reaction pathways, and overpotential. From a practical perspective, this review discusses metal‐CO 2 batteries by classifying them into reversible systems, which temporarily store and release CO 2 , and irreversible systems, which enable permanent CO 2 sequestration by coupling the discharge process with alternative anodic reactions. The former are discussed in the context of mobile and flexible energy storage applications, whereas the latter are considered for stationary integration with carbon capture, provided that challenges related to product management and economic viability can be addressed. Finally, we discuss the remaining challenges for advancing metal‐CO 2 batteries beyond model systems, including catalyst durability, operation under low CO 2 concentrations, and system‐level considerations relevant to practical implementation. This review provides a structured perspective on current limitations and outlines future research directions for metal‐CO 2 batteries.